Friday, November 23, 2007

Or at least, that's the implication of this BBC story about the latest neuroimaging paper (Fliessbach et al., 2007) in Science:

Men motivated by 'superior wage'[NOTE: so I guess women aren't, eh?we don't know, since they weren't tested]Brain scans show we measure our success by others' earnings

On receiving a paypacket, how good a man feels depends on how much his colleague earns in comparison, scientists say.

Scans reveal that being paid more than a co-worker stimulates the "reward centre" in the male brain.

What was the study actually about?

The absolute consumption level, or alternatively the absolute level of income, is the most important determinant of individual well-being in traditional economic models of decision-making. These models typically assume that social comparisons, and therefore relative income, play no role. This view has long been challenged by social psychologists and anthropologists, who have argued that comparison with other individuals is a central phenomenon within human societies...

OK, so we already know that social comparisons and relative income matter. What can we learn from this study? Is it much of a surprise that the participants were competitive?

Despite the importance of distinguishing the roles of absolute and relative income levels for subjective well-being, and thus for human decision-making, the underlying neurobiological basis of social comparison is not well understood.

Yeah, OK, stick people in a scanner and see what happens. What did the professional subjects do while there? Pairs of participants were scanned simultaneously in two different magnets while estimating the number of dots presented on a computer screen. After each trial, both participants received feedback on how each of them had done, and how much money was earned according to a predefined payment schedule. So what happened?

...conditions in which a subject solved the task correctly and received a payment while the other subject did not were contrasted with conditions in which a subject received no payment. This contrast yielded significant activation in three bilateral and three medial regions, which defined our regions of interest: left and right occipital cortex, left and right angular gyrus, left and right ventral striatum [see above figure], precuneus, and medial orbitofrontal cortex (two distinct activations), thus including the regions known to be critically involved in the processing of reward.

So all these other brain regions were activated as well. Why occipital cortex and angular gyrus? We'll never know, because the authors never discuss the significance of those responses. What was so distinctive about the ventral striatum, then?

According to our hypothesis, the parameter estimates increased with the ratio between a subject's reward and the other subject's reward... All other main effects and interactions of the ANOVA analysis turn out to be insignificant. This holds for the main effect of high versus low payment condition as well as its interaction with relative payment. The latter result suggests that the importance of relative comparison is independent of the level of payment. ... All posterior regions (occipital lobe, angular gyrus, and precuneus/cingulate cortex) showed a different pattern, with response intensity significantly varying with both absolute and relative payment. In these regions, responses were highest ... in situations when high amounts of money were unequally paid regardless of which of the subjects received more. A similar pattern was found in the two orbitofrontal regions.

In brief, the ventral striatum was uniquely related to greater relative reward (not just absolute reward). So what have we learned? It's rewarding to win a competition and to earn more money than a rival.

Reference

K. Fliessbach, B. Weber, P. Trautner, T. Dohmen, U. Sunde, C. E. Elger, A. Falk (2007). Social Comparison Affects Reward-Related Brain Activity in the Human Ventral Striatum. Science 318:1305-1308.Whether social comparison affects individual well-being is of central importance for understanding behavior in any social environment. Traditional economic theories focus on the role of absolute rewards, whereas behavioral evidence suggests that social comparisons influence well-being and decisions. We investigated the impact of social comparisons on reward-related brain activity using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject's payment affects blood oxygenation level–dependent responses in the ventral striatum. Our results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain.

Researchers released initial data today at the 60th Annual Meeting of The Gerontological Society of America (GSA) that showed that doing the right kind of brain exercise can enhance memory and other cognitive abilities of older adults.

Dr. Elizabeth Zelinski of the University of Southern California Andrus Gerontology Center presented data from the IMPACT study (Improvement in Memory with Plasticity-based Adaptive Cognitive Training) – the largest study ever done on aging and cognitive training using a program available to the public. In this prospective, randomized, controlled, double blind trial of 524 healthy adults (aged 65 and older), half the participants completed up to 40 hours of the computer-based Posit Science Brain Fitness Program. The other half, who followed the traditional advice that older adults will benefit from new learning, completed up to 40 hours of a computer-based educational training program.

The group that engaged in the Posit Science program showed significantly superior improvements in standardized clinical measures of memory gains of approximately 10 years. This is the first research study to show generalization to untrained standardized measures of memory using a publicly available cognitive training program. ...

Wednesday, November 14, 2007

Photos of Hillary Clinton elicited increased activity in the anterior cingulate cortex, a part of the brain that processes conflicting impulses, in swing voters who reported having an unfavorable opinion of her.Icons by Jennifer Daniel, New York Times

By now, anyone remotely connected to neuroimaging research knows about the new outlet for your latest sensationalistic findings: a New York Times Op-Ed piece.

But the reality is that we actually don't know what the swing voters in this experiment were thinking, and the attribution of conflicting impulses based on activity in the anterior cingulate cortex is an example of...

the logical fallacy known as "reverse inference" - inferring the participants' emotional state from the observed pattern of brain activity (Aguirre, 2003; Poldrack, 2006).

Several new critiques of the Iacoboni et al. study have appeared in these blogs:

“This Is Your Brain on Politics” (Op-Ed, Nov. 11) used the results of a brain imaging study to draw conclusions about the current state of the American electorate. The article claimed that it is possible to directly read the minds of potential voters by looking at their brain activity while they viewed presidential candidates.

For example, activity in the amygdala in response to viewing one candidate was argued to reflect “anxiety” about the candidate, whereas activity in other areas was argued to indicate “feeling connected.” While such reasoning appears compelling on its face, it is scientifically unfounded.

As cognitive neuroscientists who use the same brain imaging technology, we know that it is not possible to definitively determine whether a person is anxious or feeling connected simply by looking at activity in a particular brain region. This is so because brain regions are typically engaged by many mental states, and thus a one-to-one mapping between a brain region and a mental state is not possible.

. . .

As cognitive neuroscientists, we are very excited about the potential use of brain imaging techniques to better understand the psychology of political decisions. But we are distressed by the publication of research in the press that has not undergone peer review, and that uses flawed reasoning to draw unfounded conclusions about topics as important as the presidential election.

This article was written by Marco Iacoboni, Joshua Freedman and Jonas Kaplan of the University of California, Los Angeles, Semel Institute for Neuroscience; Kathleen Hall Jamieson of the Annenberg Public Policy Center at the University of Pennsylvania; and Tom Freedman, Bill Knapp and Kathryn Fitzgerald of FKF Applied Research.

IN anticipation of the 2008 presidential election, we used functional magnetic resonance imaging to watch the brains of a group of swing voters as they responded to the leading presidential candidates. Our results reveal some voter impressions on which this election may well turn.

Our 20 subjects — registered voters who stated that they were open to choosing a candidate from either party next November — included 10 men and 10 women. In late summer, we asked them to answer a list of questions about their political preferences, then observed their brain activity...

The participants viewed photographs of the candidates and video clips of speeches. They also filled out questionnaires before and after the scans to rate their impressions of the candidates. What were the results?

1. Voters sense both peril and promise in party brands. When we showed subjects the words “Democrat,” “Republican” and “independent,” they exhibited high levels of activity in the part of the brain called the amygdala, indicating anxiety. The two areas in the brain associated with anxiety and disgust — the amygdala and the insula — were especially active when men viewed “Republican.” But all three labels also elicited some activity in the brain area associated with reward, the ventral striatum, as well as other regions related to desire and feeling connected. There was only one exception: men showed little response, positive or negative, when viewing “independent.”

So there we have it: anxiety, disgust, reward, desire, and connectedness, all at the same time! What else?

2. Emotions about Hillary Clinton are mixed. [NOTE: really? you don't say].Voters who rated Mrs. Clinton unfavorably on their questionnaire appeared not entirely comfortable with their assessment. When viewing images of her, these voters exhibited significant activity in the anterior cingulate cortex, an emotional center of the brain that is aroused when a person feels compelled to act in two different ways but must choose one. It looked as if they were battling unacknowledged impulses to like Mrs. Clinton. [NOTE: um, this sounds a little like palm reading to me...do we actually know what the subjects were thinking while they looked at her photo?]

Subjects who rated her more favorably, in contrast, showed very little activity in this brain area when they viewed pictures of her.

This phenomenon, not found for any other candidate, suggests that Mrs. Clinton may be able to gather support from some swing voters who oppose her if she manages to soften their negative responses to her. But she may be vulnerable to attacks that seek to reinforce those negative associations.

Did we really need fMRI to tell us that Mrs. Clinton should try to soften the negative responses of swing voters?

We investigated how political party affiliation and political attitudes modulate neural activity while viewing faces of presidential candidates. Ten registered Democrats and 10 registered Republicans were scanned in an event-related functional MRI paradigm while viewing pictures of the faces of George Bush, John Kerry, and Ralph Nader during the 2004 United States presidential campaign. We found that compared with viewing one's own candidate, viewing the candidate from the opposing political party produced signal changes in cognitive control circuitry in the dorsolateral prefrontal cortex and anterior cingulate, as well as in emotional regions such as the insula and anterior temporal poles. BOLD signal in these regions correlated with subjects' self-reported ratings of how they felt emotionally about the candidates. These data suggest that brain activity when viewing a politician's face is affected by the political allegiance of the viewer and that people regulate their emotional reactions to opposing candidates by activating cognitive control networks.

Tuesday, November 06, 2007

Molecular Adaptations Underlying Susceptibility and Resistance to Social Defeat in Brain Reward Regions

Vaishnav Krishnan et al.

Summary

While stressful life events are an important cause of psychopathology, most individuals exposed to adversity maintain normal psychological functioning. The molecular mechanisms underlying such resilience are poorly understood. Here, we demonstrate that an inbred population of mice subjected to social defeat can be separated into susceptible and unsusceptible subpopulations that differ along several behavioral and physiological domains. By a combination of molecular and electrophysiological techniques, we identify signature adaptations within the mesolimbic dopamine circuit that are uniquely associated with vulnerability or insusceptibility. We show that molecular recapitulations of three prototypical adaptations associated with the unsusceptible phenotype are each sufficient to promote resistant behavior. Our results validate a multidisciplinary approach to examine the neurobiological mechanisms of variations in stress resistance, and illustrate the importance of plasticity within the brain's reward circuits in actively maintaining an emotional homeostasis.

El Dia de los Muertos, held on November 2nd is an important religous holiday in Mexico. Also called All Souls Day, it is an occasion marked by festive celebrations to honor the dead. Cemetaries are cleaned and decorated, special food and candies cooked, and home altars are designed in homage to ones ancestors. It is a day of joyous remembrance, not of sadness. The special songs, poems, foods and Day of the Dead art created for El Dia de los Muertos reflect this outlook.

About Me

Born in West Virginia in 1980, The Neurocritic embarked upon a roadtrip across America at the age of thirteen with his mother. She abandoned him when they reached San Francisco and The Neurocritic descended into a spiral of drug abuse and prostitution. At fifteen, The Neurocritic's psychiatrist encouraged him to start writing as a form of therapy.